%I
%S 1,2,2,4,6,12,18,36,62
%N Maximal size of binary code of length n and asymmetric distance 2.
%C Size of optimal singleerrorcorrecting code for Zchannel.
%C Next 3 terms are known to be in the range 112117, 198210 and 379410 respectively.
%D S. Butenko, P. Pardalos, I. Sergienko, V. P. Shylo and P. Stetsyuk, Estimating the size of correcting codes using extremal graph problems, Optimization, 227243, Springer Optim. Appl., 32, Springer, New York, 2009.
%D T. Etzion, New lower bounds for asymmetric and unidirectional codes, IEEE Trans. Inform. Theory, 37 (1991), 16961705.
%D J. H. Weber, Bounds and Constructions for Binary Block Codes Correcting Asymmetric or Unidirectional Errors, Ph. D. Thesis, Tech. Univ. Delft, 1989.
%D J. H. Weber, C. de Vroedt and D. E. Boekee, Bounds and constructions for binary codes of length less than 24 and asymmetric distance less than 6, IEEE Trans. Inform. Theory, 34 (1988), 13211332.
%H Tuvi Etzion and Patric R. J. Östergård, <a href="https://doi.org/10.1109/18.651069">Greedy and heuristic algorithms for codes and colorings</a>, IEEE Transactions on Information Theory, 44 (1998), 382388, [<a href="https://web.archive.org/web/20080612052947/http://www.tcs.hut.fi/~pat/codelist.html">Wayback Machine copy</a>].
%H N. J. A. Sloane, <a href="/A265032/a265032.html">Challenge Problems: Independent Sets in Graphs</a>
%K nonn,nice,hard
%O 1,2
%A _N. J. A. Sloane_
